Power supply circuit of an electronic component in a test machine

ABSTRACT

Power supply circuit of an electronic component in a test machine and intended to provide the component with a supply current in a given range under a nominal polarization voltage. The power supply circuit includes two identical elementary circuits each able to provide a supply current in half the given range on respective output terminals thereof which are connected in parallel. The elementary circuits each include a regulation circuit for maintaining on the electronic component a polarization voltage equal to the nominal polarization voltage, and a power circuit which is controlled by the regulation circuit to provide the supply current in half the given range. The regulation circuit of a first elementary circuit also controls the power circuit of the second elementary circuit, the power circuit of the second circuit being disconnected from the regulation circuit of the second elementary circuit.

FIELD OF THE INVENTION

The present invention concerns a power supply circuit of an electroniccomponent in a test machine.

The invention can be applied advantageously for tests, in production ordetermination of voltage vs. current characteristics, for example, formixed CMOS components (analog/digital) with an extremely highintegration scale, and more particularly those components functioningwith high currents, such as microcontrollers or microprocessors.

BAKGROUND OF THE INVENTION

Generally speaking, an electronic component test machine is mainly madeup of three elements:

a computer which is the working station enabling an operator to prepare,using an appropriate software, the test sequences he intends to conducton the electronic components, such as at the output of a productionchain, so as to check its correct functioning;

the core of a test machine, commonly known as an electronic bay,connected to the computer and which comprises a certain number ofelements for generating the test sequence prepared by the operator andfor comparing the responses obtained to those provided in advance in thecontext of a conforming functioning of the components, and

a measuring head for housing the electronic components to be tested.

Moreover, the electronic bay includes a direct current supply sub-unitformed of as many power supply circuits as needed for supplying power tothe components to be tested. Each power supply circuit is intended toprovide the electronic component in question with a direct supply ofcurrent from a given range under a nominal polarization voltage, such as+5V. Depending on the type of components to be tested, there are variouscurrent ranges characterizing the power supply circuits: there arecircuits with an extremely weak current in the range of 0 to 0.5 A, lowcurrent circuits with current in the range of 0.5 to 4 A, high currentcircuits with current in the range of 4 to 30 A, and very high currentcircuits with current in the range of 30 to 60 A.

The power supply circuits currently used having a given range are madeup of two identical elementary circuits able to provide under the samenominal polarization voltage a direct current of half the given range,the output terminals of said elementary circuits being connectedelectrically in parallel and the current applied to the electroniccomponents to be tested. For example, so as to obtain a power supplycircuit with a range having an 8 A maximum, it is thus possible whichare to place two elementary circuits in parallel low current circuitseach having a range with a 4 A maximum.

More specifically, each elementary power supply circuit firstly includesa regulation circuit intended to ensure that the voltage effectivelyapplied to the component is always equal to the nominal polarizationvoltage, and secondly a power circuit controlled by said regulationcircuit whose designated aim is to provide a direct current of half thegiven range, the total current being the sum of the currents provided bythe two elementary circuits, namely in principle double the currentprovided by each of them.

However, this type of assembly where the two elementary power supplycircuits are completely independent does have a certain number ofdrawbacks.

Firstly, on static functioning, the two elementary power supply circuitsare independent regulation circuits which, owing to dispersions ofvarious origins (components, cable length to the measuring head), do notadjust the polarization voltage identically and this causes an erraticfunctioning of one circuit with respect to the other possibly leading toa situation where an elementary power supply circuit delivers a currentinto the other elementary power supply circuit with the risk ofdestroying the other elementary power supply circuit by means of thermalrunaway without this malfunctioning being noticed by the user.

Secondly, on dynamic functioning, the presence on each regulationcircuit of an independent compensation network with the decouplingcapacitor placed on the supply pin of the component being tested cancause uncontrolled frequency stability problems due to the disparitybetween the two compensation networks. As a result, polarization voltageoscillations may occur and become unacceptable owing in particular torisks of excess heating of the component.

This difficulty linked to balancing between the two elementary circuitsis much more sensitive when it is sought to embody power supply circuitsneeding to function within a range of extremely high currents extendingup to 60 A. In fact, owing to the extremely high level of integrationreached today, the present trend is to obtain a reduction of the nominalpolarization voltage, namely a consequence of a reduction of the size ofthe components, and also an increase of the runaway current, namely aconsequence of increasing their number.

One solution to embody a power supply circuit with an extremely highcurrent would be to only use a single circuit with a single adjustmentand a single power circuit. In fact by its very definition, no problemof balancing between elementary circuits could occur. However, otherdifficulties would appear, especially as regards connectors, as it wouldbe necessary to be able to simultaneously use a larger number of pins.In addition, as the link with the component to be tested is effectedover a large distance, namely about 6 meters, so as to avoid asignificant ohmic fall occurring, it would be necessary to use a largediameter cable, which is incompatible as regards questions of spatialrequirements in relation to existing installations. Finally, componentsfunctioning under extremely high power do pose significant coolingproblems.

SUMMARY OF THE INVENTION

The solution offered by the invention is to use two elementary powersupply circuits, as in the prior art previously described, providedhowever that the problems concerning balancing by the presence of twoindependent elementary circuits are resolved.

To this effect, one aspect of the present invention provides a powersupply circuit of an electronic component in a test machine and intendedto provide said component with a direct supply current from a givenrange under a nominal polarization voltage, said power supply circuitincluding two identical elementary power supply circuits, each able toprovide on an output terminal a direct supply current from half thegiven range under said nominal polarization voltage, said outputterminals being connected in parallel at the tested electroniccomponent, said elementary power supply circuits each comprising:

a regulation circuit for maintaining on the electronic component apolarization voltage equal to the nominal polarization voltage,

a power circuit adapted to be controlled by said regulation circuit andfor providing said direct supply current from half the given range,

this arrangement being characterized in that the regulation circuit of afirst elementary power supply circuit known as the master circuit alsocontrols the power circuit of the second elementary power supply circuitknown as the slave circuit, the power circuit of said slave circuitbeing disconnected from the regulation circuit of the same slavecircuit.

Thus, the adjustment of the polarization voltage is ensured by a singleadjustment circuit, namely that of the master circuit. Thus, the causesof static and dynamic instability mentioned earlier are eliminated. Ofcourse, so as to obtain a perfect sharing of the current between themaster and slave circuits, it is essential that the power circuits areas identical as possible and that the gain, offset and thermal shiftbetween the two circuits are as small as possible with respect to thebalance sought between the currents. Note that if a significantvariation occurs at a given moment, such as a current variation, thiswould be equally supported by the two circuits.

It is also necessary to observe that even if the two elementary circuitsdo not play a symmetrical role, they are nevertheless identical, whichallows for a standardization of production of the corresponding cardswhich may derive from either slave or master circuits.

Finally, according to one advantageous characteristic of the powersupply circuit of the invention, each elementary power supply circuitcomprising at least one circuit for measuring the direct supply currentfrom half the range, the current measured by the slave circuit is addedto the current measured by the master circuit with the aid of an adderof the master circuit.

In this way, it is possible to obtain a direct measurement of thecurrent delivered by the power supply circuit, whereas in the prior artit was necessary to successively read the values of the current measuredby each circuit and then carry out addition on the computer. Thisresults in obtaining a significant gain in time.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description in relation to the accompanying drawings givenby way of non-restrictive examples shall disclose details of theinvention and on how it can be embodied.

FIG. 1 is a diagram of a power supply circuit conforming to theinvention.

FIG. 2 is a diagram of a power circuit and a measuring circuit of thepower supply circuit of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

The diagram of FIG. 1 represents the power supply circuit included in anelectronic bay (not shown) for an electronic component 1 placed in atest machine. Said component 1 is placed on the measuring head of themachine which is connected to the electronic bay by cables 3, 3′ whoselength may be about 6 meters.

The power supply circuit of FIG. 1 is intended to apply to a supply pin2 a polarization voltage Vcc which needs to be kept equal to a nominalpolarization voltage Vcco equal, for example, to +5V. Secondly, saidpower supply circuit needs to be able to provide the component 1 with adirect supply current I whose value depends on the functioning mode ofthe component, such as the stand-by mode, slight consumption mode or theworking mode in which the current may reach extremely high values of upto 60 A which defines the range of current from the power supplycircuit.

As shown on FIG. 1, the power supply circuit of the invention includestwo identical elementary power supply circuits 10, 10′ for providing ona respective output terminal 20, 20′ a direct I/2 supply current halfthe given range, such as 30 A, under said nominal polarization voltageVcco. To this effect, each elementary power supply circuit 10, 10′comprises a regulation circuit 11, 11′ for maintaining on the component1 being tested a polarization voltage Vcc equal to the voltage Vcco.Having regard to the length, about 6 meters, of the supply cables 3, 3′,it can be readily understood that the voltage Vcc effectively applied tothe pin 2 can vary, especially according to the value of the current I.Voltage adjustment is generally carried out by applying to an inputterminal 30, 30′ of the circuits 10, 10′ the voltage Vcc taken from theelectronic component 1 by a measuring line 4, 4′, the terminals 30, 30′being connected to an input of the regulation circuit 11, 11′ to whichthe nominal polarization voltage Vcco is applied provided by a voltagegenerator 12, 12′. Note the presence on the regulation circuits 11, 11′of a capacitive network 13, 13′ for compensating the uncouplingcapacitor C placed in parallel on the supply pin 2 of the component 1.

However, so as to avoid any instability which would cause an independentadjustment of the polarization voltage Vcc by each of the circuits 11,11′, as can be seen on FIG. 1, it would be an advantage for theregulation circuit 11 of the elementary circuit 10, called the mastercircuit, to perform this adjustment function. This is why the regulationcircuit 11 controls both the power circuit 14 of the master circuit 10and the power circuit 14′ of the second elementary circuit 10′, known asthe slave circuit. With this aim in mind, electronically controlledswitches 15, 15′ are inserted between the regulation circuits 11, 11′and the power circuits 14, 14′ so that the output of the regulationcircuit 11 is simultaneously connected to the inputs of the two powercircuits 14, 14′, the power circuit 14′ of the slave circuit 10′ thenbeing disconnected from the corresponding regulation circuit 11′. As theregulation circuit 11′ is out of action, the measuring line 4′ may ormay not be connected to the supply pin 2 of the electronic component 1being tested.

FIG. 1 also shows that the master 10 and slave 10′ circuits are fittedwith measuring circuits 16, 16′ for measuring the I/2 supply currentpassing through resistors 40, 40′. Operational amplifiers 42, 42′measure the voltages across resistors 40, 40′, respectively, and outputan analog signal related to the current I/2. The measured value of thiscurrent is available in a analog/digital converter 17, 17′ of eachcircuit. However, rather than successively reading the values in eachconverter and then have the computer of the test machine carry out thecalculation, it is preferable, as shown on FIG. 1, that the currentmeasured by the slave circuit 10′ is added to the current measured bythe master circuit 10 by means of the adder 18 of the master circuit 10.Electronically controlled switches 44, 44′ are controlled so that switch44 directs the output of measuring circuit 16′ to an input of adder 18while switch 44′ connects an input of adder 18′ to ground. Of course,the slave circuit 10′ also comprises an unused adder 18′ pursuant to theprinciple that even if they do not play a symmetrical role, the slaveand master circuits are completely identical for reasons ofstandardization.

As mentioned earlier, the arrangement of FIG. 1 is particularlyadvantageous for embodying a power supply circuit with a range having a60 A maximum from power circuits 14, 14′ each having a range with a 30 Amaximum which in turn can be embodied by placing in parallel twoamplifiers 14 a, 14 b each having a range with a 15 A maximum shown onFIG. 2 for the circuit 14. Of course, these two power amplifiers need tohave identical characteristics (gain, offset), and equally theirpossible temperature drifts also need to be identical. This is why theamplifiers 14a, 14b are mounted on the same heat dissipator (not shown).

Correspondingly, FIG. 2 shows that in this case, the measuring circuit16 is made up of two partial measuring circuits 16 a, 16 b whose outputsare added by an adder 16 c.

We claim:
 1. Power supply circuit of an electronic component (1) in atest machine to provide said component with a direct supply current froma given range under a nominal polarization voltage (Vcco), said powersupply circuit including a master circuit and a slave circuitrespectively including identical elementary supply circuits each able toprovide on an output terminal (20, 20′) a direct supply current from ahalf range under said nominal polarization voltage, said outputterminals (20, 20′) being coupled in parallel to the level of theelectronic component being tested, said elementary supply circuits eachincluding: a regulation circuit (11, 11′) for maintaining on theelectronic component a polarization voltage (Vcc) equal to the nominalpolarization voltage (Vcco), a power circuit (14, 14′) controlled bysaid regulation circuit (11, 11′) to provide said direct supply currentfrom said half range, wherein the regulation circuit (11) of the mastercircuit also being coupled to the power circuit (14′) of the slavecircuit, with the power circuit (14′) of said slave circuit beingdisconnected from the regulation circuit (11′) of the same slavecircuit.
 2. Power supply circuit according to claim 1, wherein, as saidgiven range is the 60 A range, the two elementary supply circuits (10,10′) from the 30 A range are each embodied via the placing in parallelof two 15 A power amplifiers (14 a, 14 b) mounted on a given heatdissipator.
 3. Power supply circuit according to claim 1, wherein aseach elementary supply circuit (10, 10′) comprises at least one directcurrent supply measuring circuit (16 a, 16 b) from the half range, thecurrent measured by the slave circuit (10′) is added to the currentmeasured by the master circuit (10) by means of an adder (18) of themaster circuit.
 4. Power supply circuit according to claim 2, wherein aseach elementary supply circuit (10, 10′) comprises at least one directcurrent supply measuring circuit (16 a, 16 b) from the half range, thecurrent measured by the slave circuit (10′) is added to the currentmeasured by the master circuit (10) by means of an adder (18) of themaster circuit.